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Agricultural land use yields reduced foraging efficiency and unviable offspring in the wild bee Ceratina calcarata

Nooten, Sabine S., Rehan, Sandra M.
Ecological entomology 2019 v.44 no.4 pp. 534-542
Ceratina calcarata, agricultural land, bees, body size, clutch size, daughters, farms, flowers, foraging, habitats, intensive farming, land use, landscapes, nesting, nesting sites, nests, overwintering, parasites, pollination, pollinators, pupae, roadsides, sex ratio, sons
1. Agricultural intensification generally leads to large‐scale habitat changes marked by decreasing availability of nesting sites and flower resources for pollinators. However, little is known about how such changes impact wild bee maternal body size and foraging effort and, more importantly, whether there is a subsequent effect on their offspring. 2. Nests were collected from the common eastern North American stem nesting bee, Ceratina calcarata, across three land management types: (i) intensely managed conventional farms; (ii) moderately disturbed organic farmland; and (iii) least managed roadsides. The study assessed the effects of land use types on body size and wing wear (a proxy for foraging effort) of maternal bees, and on their offspring in terms of clutch size, survival, sex ratio and body size. 3. Findings revealed that more brood reached pupal stages from nests collected in conventional farmlands. This was due to the total lack of parasites, possibly because the host density is below the threshold that can support a brood parasite population in intensively farmed landscapes. A positive association between maternal bee size and clutch size was only found in least managed roadsides, while, in both farm types, body sizes for daughters and sons were smaller, barely reaching the predicted overwintering threshold. 4. The results suggest that the effects of intensified agricultural land use will be more pronounced in bee offspring, potentially leading to decreased fitness for subsequent generations. This implies far‐reaching consequences for agricultural pollination services and declines in wild bee populations.